Atmospheric sampling apparatus with flexible line and probe

ABSTRACT

Arrangements for withdrawing carefully controlled samples from an active flue gas source are disclosed. A testing assembly is provided for connection to downstream processing equipment to obtain a sample from a gas stream. Included is a probe, a flexible sample line and a coupler joining the probe and the flexible sample line. At least one externally controlled or self-regulating heating cable is put in heating communication with the flexible line. A receptacle engaging the coupler is also provided for positioning the probe with respect to the flue gas source.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 11/904,952filed Sep. 28, 2007, the disclosure of which is incorporated byreference.

FIELD OF THE INVENTION

The present invention relates to the testing of atmospheric emissionsand, in particular, to testing equipment for withdrawing samples from aflue gas stream or other atmospheric discharge, especially on acontinuous testing basis.

BACKGROUND OF THE INVENTION

Owners and operators of certain combustion devices are required tocomply with a variety of environmental regulations pertaining to themaximum allowable emissions of a particular substance. One example ofsuch regulations is directed to the concentration of a substancesuspended in a waste gas, such as the flue gas of a combustion device,that discharges a waste gas stream into the atmosphere. In addition tospecifying maximum allowable amounts or concentrations, environmentalregulations at times specify how a waste gas stream is to be tested inorder to determine regulatory compliance. Taking into account thedifferent technologies and characteristics of substances involved,different testing techniques are often required for different types ofsubstances, and additionally for different timing of such testing. Forexample, testing can be periodic or continuous.

One example of continuous emission monitoring regulations is found inpart 75 of Title 40 of the Code of Federal Regulations, which pertainsto the protection of the environment by way of continuous emissionmonitoring. Subpart I of these regulations is concerned with thecontinuous emission monitoring of mercury mass emissions of certaincoal-fired units. Included in the regulations is a requirement as to howcertain aspects of the continuous emission monitoring are to be carriedout.

Compliance may be audited by a site visit for testing purposes, or acontinuous monitoring program may be required. In either event, testingcan require a substantial investment in capital and man-hours.Improvements in testing equipment, especially for repetitive (e.g.continuous) testing are continually being sought.

SUMMARY OF THE INVENTION

The present invention provides a novel and improved arrangement forwithdrawing carefully controlled samples from an active flue gas source.Equipment provided by the present invention allows easy withdrawal ofthe sample material, while leaving associated equipment, such as vacuumpumps and line heaters, undisturbed. The present invention minimizes thedisadvantages associated with prior art devices and materials relatedthereto.

One embodiment comprises a testing assembly for connection to downstreamprocessing equipment to obtain a sample from a gas stream. Included is aprobe having a first end with a gas inlet and a second end, a flexiblesample line and a coupler joining the second end of the probe and theflexible sample line. The flexible sample line includes at least one gaschannel comprising a flexible gas line coupled to the probe to transmita sample from the probe inlet to the downstream processing equipment. Atleast one externally controlled or self-regulating heating cable is putin heating communication with the flexible line. The flexible sampleline further includes an outer sheath surrounding the flexible gas lineand the heating cable, and a thermal insulator is disposed within theouter sheath and surrounds the flexible line and the heating cable.

In another embodiment, a system for controlled positioning of a probewith respect to a gas stream is provided wherein the probe has a firstend with a gas inlet and a second end for connection to downstreamprocessing equipment to deliver a sample from the gas stream. Includedis a flexible interconnect for connecting the probe to the downstreamprocessing equipment, and a coupler for joining the second end of theprobe and the flexible interconnect. The flexible interconnect includesat least one gas channel comprising a flexible gas line coupled to theprobe to transmit a sample from the probe inlet to the downstreamprocessing equipment. At least one externally controlled orself-regulating heating cable is put in heating communication with theflexible line. The flexible interconnect further includes an outersheath surrounding the flexible gas line and the heating cable. Athermal insulator is disposed within the outer sheath and surrounds theflexible line and the heating cable. A receptacle for receiving theprobe and the coupler includes a lever operated cam spaced apredetermined distance from the gas stream and engaging the coupler soas to position the gas inlet of the probe with a preselectedrelationship to the gas stream.

In a further embodiment, a flexible interconnect is provided forconnecting a probe having a first end with a gas inlet and a second end,to downstream processing equipment to obtain a sample from a gas stream.Included is a coupler for joining to the second end of the probe, atleast one gas channel comprising a flexible gas line having an inlet endfor coupling to the probe, to transmit a sample to downstream processingequipment, and at least one externally controlled or self-regulatingheating cable in heating communication with the flexible line. An outersheath surrounds the flexible gas line and the heating cable, and athermal insulator is disposed within the outer sheath so as to surroundthe flexible gas line and the heating cable.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a schematic diagram of a testing system employing the presentinvention;

FIG. 2 is a schematic perspective view of a multi-channel probe showninstalled in a flue gas stream;

FIG. 3 is an end view thereof;

FIG. 4 is an exploded perspective view thereof;

FIG. 5 is a side elevational view thereof;

FIG. 6 is a side elevational view thereof shown partly broken away;

FIG. 7 is a cross-sectional view taken along the line 7-7 of FIG. 1;

FIG. 8 is a cross-sectional view taken along the line 8-8 of FIG. 5; and

FIG. 9 is a schematic diagrammatic representation of a testing system.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The invention disclosed herein is, of course, susceptible of embodimentin many forms. Shown in the drawings, and described herein in detail, isa preferred embodiment of the invention. It is understood, however, thatthe present disclosure is an exemplification of the principles of theinvention and does not limit the invention to the illustratedembodiment.

For ease of description, a system for testing a gas stream such as acombustion flue gas stream embodying the present invention is describedherein in its usual assembled position as shown in the accompanyingdrawings and terms such as upstream, downstream, inner, outer, upper,lower, horizontal, longitudinal, etc., may be used herein with referenceto this usual position. However, the system may be manufactured,transported, sold or used in orientations other than that described andshown herein.

Flue gas sampling is one example of many industrial applications whereit is necessary to maintain the physical and chemical integrity of a gassample extracted from a process stream. Frequently, the temperature ofthe sampled gas must be maintained above a critical lower temperaturewhile it is being transported through sampling lines to downstreammeasuring devices and other equipment, in order to avoid condensation orotherwise altering important properties of the gas sample.

Conventional gas sample extraction systems are known to include a sampleprobe to be inserted directly into a process stream, such as the fluegas stream of a smokestack. A heated sample line is provided totransport the sample to downstream equipment. In many applications, gassampling systems must be carefully constructed from non-reactivematerials capable of sustaining elevated temperatures. However, certainproblems have been noted in the use of conventional equipment. Forexample, the junction where the sample probe and sample transport lineare connected must be maintained at an elevated temperature and must befree of leaks, either entering or leaving the gas sample system. Thejunction is typically embodied in a junction box, in order to meetdemanding criteria, such as the criteria discussed herein.

Referring now to the drawings, and initially to FIG. 1, a testingassembly is generally indicated at 100. Included is a flexible sampleline 102 and a generic probe 104. If desired, probe 104 and sample line102 could be made to carry only a single sampling channel. However, inthe preferred embodiment, sample line 102 and probe 104 have thecapacity to carry multiple separate, independent sampling channels, andare thus referred to herein as a multi-channel sample line and amulti-channel probe, respectively. As can be seen in FIG. 1, the sampleline 102 and probe 104 are joined, preferably permanently joined, so asto form a single unitary testing assembly.

Probe 104 and sample line 102 preferably have multiple separate andindependent gas sampling channels. In the preferred embodiment, the gassampling channels include tubing of flexible, non-reactive material suchas TEFLON or other engineered fluoropolymeric material. The flexiblelines are indicated in FIG. 1 at 110, 112. Also included are connectorsfor a variety of auxiliary equipment such as sensors and heaters.Included are connectors 114, 116 associated with each flexible line anda connector 118 associated with instrumentation separate from theflexible lines.

Probe 104 can comprise virtually any type of probe known today, havingeither single or multiple channel capability. As mentioned, in apreferred embodiment, probe 104 has multi-channel gas samplingcapability and includes a pair of gas sampling channels. Referring toFIG. 2, the gas sampling channels have inputs 120, 122. A thermocouple124 is also located adjacent gas inputs 120, 122. In the preferredembodiment, probe 104 is designed to have a specialized gas samplingcapability, to withdraw gas samples using absorbent material. In apreferred embodiment, probe 104 utilizes sorbent trap technology.

Referring briefly to FIG. 4, included in probe 104 is a sorbent trap 130with an insert including sections 132 of sorbent trap material. Althoughnot required, the sorbent trap insert 130 is received within an outershell 136 of rugged stainless steel construction. A ferrule orfrustoconical collar 138 is attached, preferably by welding or brazing,to the inlet end of shell 136, and a nut or compression fitting 140 thatthreadingly engages a threaded nipple 142 which is fitted to an end cap144 of a rugged stainless steel housing 146 of probe 104. In a preferredembodiment, the compression fitting 140 can be removed for readywithdrawal of a sample cartridge 152 formed by the combination ofsorbent trap insert 130, outer shell 136 and, as an option, fitting 140.The sorbent trap insert 130 may be easily withdrawn from shell 136 withthe shell 136 either removed from housing 146 or left in place as shown,for example, in the adjacent gas sampling channel having input 122.However, virtually any sample probe arrangement can be utilized with thepresent invention and removable inserts and/or removable cartridgeassemblies are not required.

Referring to FIGS. 5 and 6, the downstream ends 150 of the sorbent trapinserts 130 are coupled to flexible lines 110, 112 (see FIG. 1) in amanner (not shown) to form a continuous gas sampling passageway. As willbe seen herein, auxiliary equipment such as thermocouples and heatersare combined with the gas passageways to form a pair of gas samplingchannels.

Referring now to FIG. 7, a cross-sectional view of sample line 102 isshown. Included in the sample line 102 are two gas sampling channelsgenerally indicated at 154, 156. Included in each channel are flexiblehollow lines 110, 112 which, as mentioned above, are preferably made ofTEFLON material. Surrounding the flexible lines 110, 112 is an outercovering 162 of thermal barrier material such as fiberglass cloth, whichis coated, wrapped or otherwise disposed about each flexible line. Asindicated in FIG. 7, the channels 154, 156 are spaced apart and disposedwithin a rugged outer weatherproof jacket 166 of polyurethane material.The outer jacket 166 is preferably formed with a shrink-wrap process.The interior of sample line 102 is filled with a thermal insulatormaterial such as glass fiber insulation and most preferablynon-hygroscopic glass fiber insulation material indicated at 168.

Also included in each gas channel is a externally controlled orself-regulating heater preferably in the form of electrical cablesschematically indicated at 172. Preferably, each flexible line iswrapped with two independent externally controlled or self-regulatingelectric resistance cable heaters. The length of the first heater cableis equal to the length of the flexible line that is inserted into theprocess stream. The second heater cable is wrapped around the length offlexible line that remains outside of the process stream. As indicatedin FIG. 7, the heater cables are encapsulated in insulation material168. In the preferred embodiment, the two heaters for each gas channelprovide an arrangement for maintaining two temperature zones. One zoneis the section of the sample line that is covered by the probe sheath orouter probe housing 146. This section is exposed to the process gas andmust maintain the proper sample gas temperature while being exposed tothe temperature of the process gases. The second heated zone is thesection of the flexible line that transports the extracted sample todownstream equipment such as a gas conditioning and pumping system ofthe type generally indicated in FIG. 9 to be discussed below. The secondheated zone maintains the proper gas temperature while being exposed toambient air temperature.

The section of the sample line 102 that is inserted into the processstream is wrapped with a high temperature protective jacket of siliconematerial. This section is placed inside the rigid stainless steel tubeforming the outer housing 146, shown in FIG. 4. As mentioned, thehousing 146 at the free end of the probe is joined to an end wall 144,preferably by welding, brazing, or other metallurgical joinder. Thatportion of sample line 102 that remains outside of the process gas iswrapped with the weatherproof protective jacket 166 (see FIG. 7).

In a preferred embodiment, sample line 102 contains instrumentation forthe operation of the testing assembly. Included are a number ofthermocouples measuring different operating parameters. Thethermocouples are accessed by connectors 114, 118 shown in FIG. 1.Referring again to FIG. 7, a line thermocouple 180 is provided tomeasure the internal temperature of sample line 102. As mentioned withreference to FIG. 2, a thermocouple 124 is provided for sensing thetemperature of the process gas and is placed in-situ in the gas streamadjacent gas inlets 120, 122. The signal for this thermocouple iscarried by electrical conductor 182 shown in FIG. 7. Connection with thethermocouple is made with connector 118 in FIG. 1. As mentioned, thesorbent trap inserts 130 are located in probe 104. Preferably, thetemperature of the sorbent traps are monitored by their own respectivethermocouples, with signals being transmitted through electricalconductors 186, 188 to a pair of connectors 114 as shown in FIG. 1.

Referring now to FIG. 8, a section of probe 104 is shown schematicallyin cross-section. Included are the sorbent trap inserts 130, preferablyin the form of hollow glass tubes receiving sections of sorbent trapmaterial 132, separated from one another by separator sections 134 asshown for example in FIG. 4. Referring again to FIG. 8, the outer shell136 of the sorbent trap cartridge surrounds the sorbent trap inserts130. Electrical conductors 192 for thermocouple 124 are located in theupper portion of FIG. 8 and electrical conductors 194 are provided foradditional instrumentation. The interior of the probe is filled withthermal insulation which, as mentioned, preferably comprisesnon-hygroscopic glass fiber insulation. As shown in FIGS. 7 and 8, isthe outer jacket 166 is preferably located immediately inside of therigid, stainless steel housing 146.

There are many applications involving the direct insertion of sorbenttraps into an industrial gas stream to measure properties of the gasstream. One application, for example, requires the measurement of atrace component, such as mercury concentrations, using sorbent traps.Sorbent traps may include, for example, glass tubes packed withiodinated activated carbon. As mentioned in greater detail herein, oneprotocol for this measurement is contained in the alternative mercurymonitoring approach detailed in 40 C.F.R. 75, Appendix K.

Usually, sorbent trap sampling requires forming and maintaining agas-tight seal between the traps and the physical device used to holdthem in place during sampling, herein referred to as a sorbent trapmodule or probe. This arrangement allows a vacuum to be placed on theapparatus during sampling and any leakage between the trap and theapparatus could lead to erroneous sampling results. For example, inAppendix K applications, the gas seal, such as that provided by thepresent invention must be able to maintain leak tightness at a minimumvacuum of 15 inches Hg absolute pressure. Additionally, the sealprovided by the present invention is able to withstand chemical andphysical conditions of the environment inside the gas stream which, aswill be apparent to those skilled in the art, may often times be hot,corrosive and/or dust-laden.

Sorbent trap modules or probes according to principles of the presentinvention allow sorbent trap inserts to be quickly inserted and removedfrom the probe without the use of tools. The trap or insert is pushed byhand into a removable module inside the probe, preferably in the form ofcartridge 152 shown for example in FIG. 6. A leak-tight seal is madebetween the insert 130 and the shell 136 of cartridge 152 by a series ofthree o-rings 126, preferably contained within interior grooved ringsformed inside of cartridge shell 136 in the manner indicated in FIG. 1.The probe 104 and cartridge 152 preferably include outer housings madeof stainless steel or another type of corrosion-resistant ridgedmaterial. Preferably, the o-rings 126 are made of a pliable, chemicallyresistant and thermally stable polymer such as silicone or VITON. Thecartridges 152 are held in place within the probe and sealed to theprobe using a threaded compression fitting and nut assembly 142, 138 and140, respectively.

Accordingly, the sorbent traps, i.e., sorbent trap inserts 130 can beinserted and removed without the need for tools such as wrenches orpliers. With the present invention, the sampling process is simplifiedand is made more time efficient. The sorbent trap module or cartridge152 can be readily removed from probe 104 and replaced with a new one,as may be desired. The nut 140 used to hold the cartridge in placewithin probe 104 may be tightened and loosened with a wrench, but,according to a preferred embodiment, the cartridge 152 is not removedfrom the probe 104 except for periodic maintenance purposes, such aso-ring wear. In this regard, it is generally preferred in the presentinvention that three o-rings are provided to seal the sorbent trapinsert 130 and to provide redundancy in case of failure of a particularo-ring. Further, as can be seen for example in FIG. 1, it is generallypreferred that two o-rings be placed close to each other at thedownstream end 150 of the sorbent trap insert and that a single o-ringbe located at the forward or free end of probe 104, adjacent the gasinlet end 120 of the sorbent trap insert.

With reference to FIG. 6, the test assembly 100 conveniently provides amultichannel, redundant testing capability which is often a conditionfor a regulatory body to allow self-testing programs implemented by thefacility operator, rather than a designee or member of the responsibleagency. In order to provide maximum benefits to an operator, the testingassembly should be relatively lightweight and for the most part reusablefrom one testing operation to another. This is particularly importantwhere continuous or quasi-continuous monitoring is required. Severaltimes a day, during continuous operation of the facility, examples arewithdrawn from the gas stream, an operation often repeated during thelife of the facility, especially since many large scale facilities areseldom completely shut down.

As mentioned above, the probe 104 is preferable made rigid and withlocating fitting 218, allows the accurate positioning of inlets for thegas sample channels within the gas stream flow to be tested. However, inlight of the need for gas-tight seals to be continuously maintainedduring testing and the need for flexibility to allow the probe to bepermanently joined to the sample line 102, it is important that thesample line be made relatively flexible, without compromising leak-freeintegrity of the test assembly. The preferred construction describedabove with reference to FIG. 7, for example, allows sample line 102 tomeet these criteria while being relatively lightweight. The materialsand dimensions of one example of a testing assembly have been givenherein and afford a relatively lightweight construction, typically onthe order of three pounds per linear foot.

With testing assemblies according to principles of the presentinvention, the exposed portions of the trap inserts, at the inlet to thegas channels, may be carefully controlled and protected by an operatorfrom accidental contact and breakage, when contacting a nearby object.It should be remembered, in this regard, that often testing facilitiesare not typically provided for during design and construction of thefacility but rather are added later, where space and other conditionsallow. Further, testing operations are conducted, in many instances,continuously, year-round. In very cold weather when gloves and otherprotective apparel are required, the ability to control the free end ofprobe 104 and the exposed glass tubes projecting therefrom, becomes evenmore important. The flexible sample line 102, the construction of therigid probe 104, the precision positioning fitting 218 and thereceptacle construction 202 all contribute to ensure that continuoustesting programs and other testing procedures can be successfullycarried out, even during extreme atmospheric conditions.

The testing assembly according to the principles of the presentinvention provides a compact, relatively lightweight arrangement whichaids in obtaining gas samples in difficult work areas of restrictedaccessibility such as may be provided about a smokestack of an operatingcombustion facility. For example, in one preferred embodiment accordingto the present invention, the outer housing 146 of probe 104 has a 2.5inch outer diameter and sample line 102 has an outer diameter of similardimensions. The sorbent trap inserts 130 are made of hollow glass tubinghaving an outer diameter of about 0.39 inches and an inside diameter ofapproximately 0.32 inches. The walls of outer shell 136 of the cartridge152 preferably have a thickness of approximately 0.09 inches and alength of approximately 8.5 inches. The flexible lines 110, 112preferably have an approximate nominal external diameter ofapproximately one quarter inch.

Turning again to FIG. 1, a fitting assembly generally indicated at 202is provided for support and control of depth insertion of the probe inthe process stream. Included in assembly 202 is a port 204 and flange206. Connected to flange 206 is a pipe nipple 208 which preferably has anominal internal diameter of 2.5 inches. Also included is a quick lockfitting 210 with an internal bore of approximately 2.5 inches,dimensioned to receive probe 104. A pair of cam locks (not shown)protrude into the inner bore of fitting 210 and are operated by leverarms 212. The cam members seat against a grooved portion 216 of afitting 218 mounted at one end of probe 104 and are preferably rigidlyconnected thereto by welding, brazing or other form of metallurgicaljoinder. A flexible, high-temperature o-ring 211 (e.g., Viton) sits in agroove within the fitting 210 and seals against fitting 218 when the camlocks are engaged.

Fitting 218 is in turn connected to sample line 102 and a strain reliefsystem 222 is provided to transfer support load to assembly 202. Inoperation, probe 104 is inserted into fitting 210 so as to project intothe process flow in the manner indicated in FIG. 2. Preferably, fitting218 provides an approximate insertion limit by engagement with fitting210. The final insertion control is provided when the cam locks areoperated by lever arms 212 with the cam locks received in groove 216 toprovide a final, rigidly secure and accurately positioned engagement ofthe probe with respect to the process stream.

Although a particular probe construction has been described above, thetesting assembly according to principles of the present invention canreadily employ probes of different constructions and operatingprinciples. Further, those skilled in the art will readily appreciatethat the sample line can be readily modified to accommodate differentnumbers of gas channels to be monitored. For example, a single channelcan be readily provided as can a system having three or more gaschannels. Further, the present invention can be employed to testvirtually any type of material.

Referring now to FIG. 9, a sample system suitable for use with theaforementioned probe, sample line and related equipment is generallyindicated at 10. Included is a duct wall 12 confining a gas stream whichflows in the direction of arrow 14. An entrance 16 formed in duct wall12 is provided for probe 20. In one example, probe 20 includes a sorbenttrap 22 which is placed in the gas stream. A pump 26 draws flue gasthrough trap 22 and probe 20. That portion of the gas stream passingthrough trap 22 is drawn through a chiller 30 and desiccant unit 32before entering subsystem 34 which includes pump 26. An isolation valve40 and flow control valve 42 are provided along with a flowcontroller/data logger 44 which outputs data on port 46. Gas streamleaving pump 26 passes through dry gas meter 50 and a rotating meterdevice 52 before being discharged at 54.

The foregoing descriptions and the accompanying drawings areillustrative of the present invention. Still other variations andarrangements of parts are possible without departing from the spirit andscope of this invention.

1. A testing assembly for connection to downstream processing equipmentto obtain a sample from a gas stream, comprising: a probe having a firstend with a gas inlet and a second end; a flexible sample line; a couplerjoining the second end of the probe and the flexible sample line; theflexible sample line including at least one gas channel comprising aflexible gas line coupled to the probe to transmit a sample from theprobe inlet to the downstream processing equipment; at least one heatingcable in heating communication with the flexible line; the flexiblesample line further including an outer sheath surrounding the flexiblegas line and the heating cable; and a thermal insulator disposed withinthe outer sheath and surrounding the flexible line and the heatingcable.
 2. The testing assembly according to claim 1 further comprising afirst thermocouple in heat sensing communication with the probe andhaving output conductors carried by the flexible sample line.
 3. Thetesting assembly according to claim 1 further comprising a secondthermocouple in heat sensing communication with the gas line and havingoutput conductors carried by the flexible sample line.
 4. The testingassembly according to claim 1 further comprising a third thermocouple inheat sensing communication with the flexible sample line and havingoutput conductors carried by the flexible sample line.
 5. The testingassembly according to claim 1 wherein the coupler has a positionindexing surface located at a preselected distance from the gas inlet.6. The testing assembly according to claim 1 wherein the coupler has anannular groove defining said indexing surface.
 7. The testing assemblyaccording to claim 1 wherein the probe has a plurality of gas inlets andthe flexible sample line has a plurality of gas channels coupled to theprobe to transmit samples from the probe inlets to the downstreamprocessing equipment.
 8. The testing assembly according to claim 7wherein gas channels are spaced apart, one from the other.
 9. A flexibleinterconnect for connecting a probe having a first end with a gas inletand a second end, to downstream processing equipment to obtain a samplefrom a gas stream, comprising: a coupler for joining to the second endof the probe; at least one gas channel comprising a flexible gas linehaving an inlet end for coupling to the probe, to transmit a sample todownstream processing equipment; at least one heating cable in heatingcommunication with the flexible line; an outer sheath surrounding theflexible gas line and the heating cable; and a thermal insulatordisposed within the outer sheath and surrounding the flexible gas lineand the heating cable.
 10. The flexible interconnect of claim 9 furthercomprising an output conductor for a first thermocouple in heat sensingcommunication with the probe, carried by the flexible interconnect. 11.The flexible interconnect according to claim 9 further comprising asecond thermocouple in heat sensing communication with the flexible lineand having output conductors carried by the flexible interconnect. 12.The flexible interconnect according to claim 9 further comprising athird thermocouple in heat sensing communication with the gas line andhaving output conductors carried by the flexible interconnect.
 13. Theflexible interconnect according to claim 9 wherein the coupler has aposition indexing surface located at a preselected distance from the gasinlet.
 14. The flexible interconnect according to claim 9 wherein thecoupler has an annular groove defining the indexing surface.
 15. Theflexible interconnect according to claim 9 wherein at least one heatingcable is wrapped about the gas line
 16. The flexible interconnectaccording to claim 9 wherein the gas line has a rigid self supportingconstruction under vacuum, whereby the sample may be transported alongthe flexible interconnect without requiring external support for the gasline to resist collapse when carrying a vacuum signal.